To the extent of my knowledge the batteries between our cars were all the same. Maybe some differences between the pre98s and the later models but I doubt very much. Even if the P/N is different, as long as the specs are the same it doesn't really matter.
Sockdolloger,
Are you still using your original battery? If so it is probably on its way out. Consider gettting new wires and a new ignition coil too. Accel makes a replacement coil that should make a difference in your performance. Wires could always help also. Batteries can be expensive so it's really up to you where you go from here...if the battery is original I'd bet that, coupled with the other original ignition parts, the battery is the main problem.
If you're interested I still have my stock ignition coil from my 98, it has about the same mileage as you do on it. If you'll pay the shipping I could send it to you and see if it makes a difference at all...if so we can go from there...if not just send it back and we'll have narrowed down a possibility.

HTH.